The invention relates to a method for the manufacture of welded composite panels from at least two sheet-metal pieces. The invention also relates to an apparatus for the manufacture of welded composite panels from at least two sheet-metal pieces.
It is known to join sheet-metal pieces together by welding, particularly by laser welding, to form larger sheet-metal panels known as xe2x80x9ctailored blanksxe2x80x9d (Platinen). These composite panels, usually formed from sheet-metal pieces of different thicknesses and/or material properties, are then shaped e.g. into formed components for the motor vehicle industry which have locally dissimilar properties adapted to their loading. Examples of such formed components are side members contributing to the crumple zone in the VW Golf, or the side wall of the Chrysler Cherokee. However, the invention is not limited to the manufacture of tailored blanks for the motor vehicle industry.
EP 532835 discloses a welding machine for the manufacture of tailored blanks, hereinafter also called TB. The word xe2x80x9ctailoredxe2x80x9d refers to the predefined shape of the individual sheet-metal parts, and also of course to that of the welded assembly, these shapes being optimized in terms of both geometry and alloy for the subsequent application (structural members in the crumple zone or side wall). As presented in that publication, two sheet-metal pieces with predetermined shapes are in each case welded together (though one of the sheet-metal pieces may of course itself consist of parts that have already been welded together). For a typical TB consisting originally of four sheetmetal parts A, B, C and D, three welding operations are necessary. For example, two welding machines might be set up side by side to join the parts A and B to form the part AB, and the parts C and D to form the part CD, these parts AB and CD then being welded together by a third machine to form the TB. Handling between welding machines is usually performed by robots. Even with a crowded-together and optimized construction, such a welding installation can easily occupy a machine shop measuring 35xc3x9722 m (the individual welding machine can be 4xc3x976 m); see also EP A 743129 or EP 522811, in particular the layout in FIG. 6, regarding the loading of an individual welding machine; and for a level of production such as exists in the motor vehicle industry, there may be a need for two or three installations running in parallel. Depending on production in the motor vehicle factory, these installations could be operating on a three-shift system. Special logistical requirements then arise, be they in the feed of individual sheets to the installation, manipulation within the installation, or onward transport of completed TBs from the installation. Firstly, problems are caused by the dimensions of the metal sheets which may run to several meters, the tonnages of the stacks of sheets, and the vulnerability of the sheet edges to be worked on. Secondly, storage is usually impossible or highly undesirable, as the just-in-time principle has to be observed and the quantities to be stored for production of up to several thousand vehicles per day (e.g. VW Golf III and IV) are so large as to be logistically difficult and therefore cost-intensive. Simplifying the logistics, in both small and large installations, is a constant concern. For want of alternatives, efforts are being concentrated on precise production planning and on optimizing the layout of the installations and the production facilities as a whole.
In the present state of the art, the welding of pieces to make a composite panel is performed in the flat horizontal (downhand) position, on corresponding welding installations constructed for holding the pieces, as shown highly schematically in FIG. 1 by way of example. The laser beam 2 of the installation 1 which acts on the joint line of the pieces 5, 5xe2x80x2 from above is produced by a laser 3, and impinges on the horizontal pieces which are held in the welding position on a holding device 7 magnetically or pneumatically and also, if need be, mechanically, and are usually traversed under the laser in the direction at right angles to that of the laser itself which is traversable in one direction only.
The remainder of the known processing steps (stamping of beads, possibly cutting) and also conveying and (interim) storage are performed with the pieces or panel in the horizontal position.
Handling of the horizontally-held composite panels, which in some cases may have large dimensions, e.g. 200xc3x97200 cm or larger, requires a considerable amount of room, and the composite panel is generally accessible only from above.
The fundamental task of the invention is to provide a method and an apparatus of the kind stated at the outset which do not have these drawbacks and which improve the construction and operation, respectively, of the installation.
The present invention resides in the method of manufacture of laser-welded composite panels from at least two sheet metal pieces. The pieces have at least one processing step in which the pieces or composite panels are first placed in an essentially upright position and then held in that position for further processing.
In a further aspect of the invention, the invention comprises an apparatus for the manufacture of composite panels from at least two sheet-metal pieces. The apparatus for processing the pieces has an essentially upright configuration and includes a holding device for the sheet metal pieces that stands upright or is tilted into an upright position. The apparatus further comprises a welding plant that is configured to generate a laser welding beam emitted essentially horizontally with respect to the floor area of the holding device and welding plant.
Working with the composite panels or pieces in the upright position results in a large saving of space (the room required in the vertical direction is usually available anyway), and better access to the composite panels.
Preferably, as processing step, welding is performed with the pieces or panel in the upright position.